The present invention relates to sprinkler heads used in automatic fire extinguishing systems for buildings and the like, and in particular, relates to a trigger assembly for a quick response automatic sprinkler head.
Sprinkler heads have long been used in automatic fire extinguishing systems in order to controllably disburse a fluid to suppress or extinguish a fire in a designated area. Typically, the fluid utilized in automatic fire extinguishing systems is water, however, systems have also been developed to disburse other fire extinguishing fluids. In one common design, sprinkler heads include a sprinkler body having a central orifice with an inlet connected to a pressurized supply of water or other fire extinguishing fluid, and an outlet through which the fire extinguishing fluid is expelled. A frame extends from the sprinkler body and projects a preselected distance beyond the outlet of the central orifice. The frame carries a deflector designed to alter the water trajectory in an optimum pattern. The sprinkler head may be coupled to a fluid supply line such that the sprinkler head extends in an upward direction towards the ceiling of the structure, in which case it is referred to as an “upright” sprinkler head. Alternatively, sprinkler heads are characterized as “pendent” when the sprinkler head is coupled to a fluid supply line such that the sprinkler head projects towards the floor. Also, a side wall sprinkler head is defined as one which projects substantially orthogonally from a side wall of an enclosure.
In the non-activated state, water flow through the central orifice is prohibited by the presence of a sealing assembly which sealingly engages the outlet. A trigger assembly, positioned between the sealing assembly and the deflector, imparts a force upon the sealing assembly to maintain its sealing position within the orifice outlet. To maintain the sealing assembly within the orifice outlet, a compression screw or other rotatable member is rotatably positioned within a boss formed at the frame's apex. When rotated, the compression screw places a compressive force upon the trigger assembly, which forces the sealing assembly into the orifice outlet.
In one common design, the trigger assembly is composed of a glass bulb filled with a fluid having a known thermal expansion profile. The glass bulb is oriented between the sealing assembly and the frame's apex, and is placed in compression by the compression screw. The glass material employed must be capable of withstanding the substantially axial load placed thereupon by the compression screw. When the glass bulb is exposed to an elevated temperature indicative of a fire, the fluid encased therein will expand, due to an increase in pressure, causing the rupture or fracture of the glass bulb. Once the glass bulb is fractured, the pressurized water residing within the central orifice expels the sealing assembly from the orifice outlet.
In another common design, the trigger assembly includes a pair of lever arms, each of which is in contact with either the compression screw or the sealing assembly. The lever arms are joined by a fusible link normally including a pair of plates joined by a fusible material such as solder. The lever arms are placed in a biased position by the compression screw and are held in place by the presence of the fusible link. In response to a fire, the solder fuses, relaxing the plates of the fusible link, which in turn releases the levers from their biased position, and results in the actuation of the sprinkler head.
In the 1970's, given the advent of new materials and structures frequently utilized in both business and industrial environments, it was recognized by the sprinkler industry that in certain circumstances, standard or normal sprinklers were incapable of adequately controlling fires in areas containing these newer materials and structures. Specifically, it was found that these materials, subsequent to ignition, rapidly spread the conflagration to surrounding areas before the standard sprinkler head could initiate a suppressive water flow. Hence, in many instances, the standard sprinkler trigger assembly failed to have adequate sensitivity necessary to timely activate the sprinkler head and thus, control the fire. Frequently, the trigger assembly lack of thermal sensitivity was attributed to the design utilizing a pair of levers joined by a fusible link.
In response to the inability of standard sprinklers to effectively combat fires having the newer materials which combust and burn at a faster rate, the industry advanced what is commonly known as “quick response sprinkler heads.” The purpose of quick response (“QR”) sprinkler heads is to provide a greater sensitivity in the trigger assembly so as to reduce the time period between ignition of the fuel package and the activation of the sprinkler head and thereby prevent the fire from spreading to surrounding areas. These quick response sprinklers normally utilize a glass bulb trigger assembly.
In order to provide uniformity in what constitutes a quick response sprinkler head, the National Fire Protection Association (hereinafter referred to a the “NFPA”) generates criteria or regulations for the design of fire sprinkler heads, as well as the installation of fire sprinkler systems. The NFPA is comprised of a wide cross-section of companies and organizations having an expertise and interest in fire protection safety. The NFPA regulations or guidelines are based on data gained by over 100 years of experience in the evaluation of sprinkler systems. Compliance with the NFPA guidelines is frequently required by federal and state enforcement agencies, and is accepted by the insurance industry as one of the definitive guidelines concerning sprinkler head design. Consequently, as a commercial reality, failure of a sprinkler head design to operate successfully within the parameters set by the NFPA effectively prohibits the commercial exploitation of the design.
Section 1.4.5.2 of NFPA 13 (1999 Ed.) defines a quick-response (QR) sprinkler as follows:                A type of spray sprinkler that meets the criteria of 1-4.5.1(a)(1) and is listed as a quick response sprinkler for its intended use.        
Section 1-4.5.1 of NFPA 13 (1999 Ed.) states as follows:                1-4.5.1 The following are characteristics of a sprinkler that define its ability to control or extinguish a fire.                    (a) Thermal sensitivity. A measure of the rapidity with which the thermal element operates as installed in a specific sprinkler or sprinkler assembly. One measure of thermal sensitivity is the response time index (RTI) as measured under standardized test conditions.                        1. Sprinklers defined as fast response have a thermal element with an RTI of 50 (meters-seconds)1/2 or less.        
Thus as is clear from the above sections of NFPA 13 (1999 Ed.), the ability of a sprinkler head to perform successfully as a quick response sprinkler requires that the trigger assembly have a response time index of 50 (meters-second)1/2 or less. The lower the RTI value of a particular sprinkler head, all other variables being equal, the faster the actuation time of the sprinkler head. That is, as the RTI value decreases, the time period between ignition of the fuel package and the subsequent actuation of the sprinkler head decreases, which, in consequence, increases the ability of the sprinkler head to control or suppress the fire and prevent the conflagration from spreading to adjacent areas. The entire NFPA 13 (1999 Ed.) is hereby incorporated herein by reference.
Another organization which promulgates regulations and guidelines concerning fire sprinkler systems, and performs approval tests for such systems is Underwriter's Laboratory, Inc. (hereinafter referred to as “UL”). UL standards are an additional body of regulations which are commonly accepted and relied upon by the fire sprinkler industry, insurance companies, and many state and federal enforcement agencies. As with the NFPA, conformance of a sprinkler head design with the guidelines promulgated by UL, is a practical necessity for the commercial viability of a sprinkler head design.
Section 3.3.12 of UL 199, Automatic Sprinklers for Fire Protection Service (10th Ed., 1999) defines a QR sprinkler as follows:                A sprinkler that complies with the applicable requirements for such sprinklers in the Sensitivity Test, Section 19, and that is intended to be installed at standard spacings.        
Section 19 of UL 199 (10th Ed., 1999) states in pertinent part, the following:                19.1 General.        19.1.1 An automatic sprinkler, other than a dry-type, shall comply with the following requirements:                    d) 19.2.1 and 19.5.1 for QR and QR extended coverage sprinklers.                        
Section 19.2 of UL 199 states as follows:                19.2 Sensitivity-oven heat test        19.2.1 A QR sprinkler shall have the following operating time characteristics when tested in the sensitivity test oven as specified in 19.2.3-19.2.5:                    a) Fourteen seconds or less for each sprinkler when subjected to the test in 19.2.3.            b) Mean time equal to or less than a 1.30 multiple of the mean time of the sprinkler tested in accordance with (a) after being subjected to the exposure tests specified in Sections 23, 26, 28, and 35.                        
Sections 19.2.3 through 19.2.5 of UL 199 state as follows:
Sprinklers of each style are to be tested in the sensitivity test oven in the pendent position with the heat responsive element located at least 1 inch (25.4 mm) away from the inside surfaces of the oven as follows:                a) For sprinkler designs without frame arms and incorporating symmetrical heat responsive elements and symmetrical sprinkler bodies, ten samples are to be orientated in the pendent position.        b) For sprinkler designs with or without frame arms and incorporating unsymmetrical heat responsive elements or unsymmetrical body designs, ten samples are to be orientated in the pendent position with the heat responsive element upstream of the axis of the sprinkler body.        c) For sprinkler designs incorporating frame arms with symmetrical heat responsive elements, ten samples are to be orientated in the pendent position with the frame arms in a plane perpendicular to the direction of air flow.        d) For ceiling style sprinkler designs incorporating removable cups, escutcheons, and removable closure assemblies, ten samples are to be orientated in the pendent position with the closure assemblies removed. For ceiling style sprinkler designs incorporating an integral closure assembly, ten samples are to be orientated in the pendent position with the heat responsive element exposed to the air flow.        
19.2.4 The samples are to be conditioned at 75±2° F. (24±1° C.) for at least 2 hours. The inlet end of each sprinkler sample is to be connected to a source of air pressure at 4±1 psig (28±7 kPa) and quickly plunged into the sensitivity test oven in a pendent position. Each sprinkler is to be observed to determine if operation occurs as intended within the time specified in 19.2.1.
19.2.5 The sensitivity test oven is to consist of an 8 inch (203 mm) square stainless steel chamber as shown in FIG. 19.1. A constant air velocity of 8.33±0.05 feet per second (2.54±0.01 m/s) and an air temperature as specified in Table 19.1 for each temperature rating and style sprinkler are to be established. Air velocity is to be measured using an orifice plate and a manometer or a bidirectional probe and a velometer. The air temperature is to be measured by use of a No. 30 AWG (0.05 mm2) thermocouple centered upstream from the sprinkler as shown in FIG. 19.1.
FIG. 19.1, referenced in Section 19.2.5 of UL 199 is reproduced herein as FIG. 1.
Section 23 of UL 199 reads as follows:                23 High Temperature—Test for Uncoated Sprinklers        23.1 An uncoated automatic sprinkler shall withstand for 90 days, without evidence of weakness or malfunction, an exposure to a high-ambient temperature in accordance with Table 23.1, or 20° F. (11° C.) below the rated operating temperature of the samples (whichever is the lower temperature), and not less than 120° F. (49° C.). Following the exposure, each sprinkler shall comply with the Leakage Test, Section 14. Sprinklers of other than the dry type and QR recessed, QR concealed, QR-EC recessed, and QR-EC concealed are to then be subjected to the Sensitivity—Oven Heat Test, see 19.2.1-19.2.5. The Sensitivity—Room Heat Test is to be conducted on QR recessed, QR concealed, QR-EC recessed and QR-EC concealed type sprinklers, see 19.5.1-19.5.5; and the Response Test for Ordinary and Intermediate Temperature Rated Ceiling Type Sprinklers is to be conducted on standard response type recessed and concealed sprinklers, see 19.3.1-19.3.5. Each sample shall be operable, and the average time of operation shall not increase more than a 1.3 multiple when compared to the average time of samples not subjected to the High Temperature—Test for Uncoated Sprinklers. Dry-type sprinklers are to then be subjected to the plunge test described in 35.3.        
Table 23.1, referenced in Section 23.1 of UL 199 is set forth herein as FIG. 2.
Section 19.5.1-19.5.5, referenced in Section 23.1, is as follows:
19.5.1 Ordinary or intermediate temperature rated QR sprinklers and QR extended coverage sprinklers for light hazard occupancies shall have an operating time of 75 seconds or less for each sprinkler when tested as specified in 19.5.3-19.5.5. Ordinary or intermediate temperature rated QR extended coverage sprinklers for ordinary hazard occupancies shall have an operating time of 55 seconds or less for each sprinkler when tested as specified in 19.5.3-19.5.5.
19.5.2 A recessed or concealed sprinkler having a vented escutcheon is to be installed and tested in an unblocked manner, that is, in a manner that does not inhibit air flow through the escutcheon.
19.5.3 Sprinklers of each type are to be installed in a test room (see 19.5.4) in the following position and orientation:                a) For pendent and ceiling type sprinkler designs without frame arms and incorporating symmetrical heat responsive elements and symmetrical sprinkler bodies, ten samples are to be installed in their intended position at the ceiling.        b) For pendent and ceiling type sprinkler designs with or without frame arms and incorporating unsymmetrical heat responsive elements, ten samples are to be orientated with the heat responsive element downstream of the axis of the sprinkler body in relation to the direction of the fire source. The samples are to be in their intended position.        c) For pendent and ceiling type sprinkler designs incorporating frame arms with symmetrical heat responsive elements, ten samples are to be orientated with the frame arms in a plane parallel to the direction of the fire source. The samples are to be installed in their intended position.        d) For upright sprinklers having configurations referenced in (a), (b), and (c), ten samples are to be installed in the pendent position.        e) For sidewall sprinkler designs, ten samples are to be installed in their intended position with the deflector located 4 inches (102 mm) below the ceiling.        
19.5.4 The sprinkler is to be mounted as specified in 19.5.3 on a ceiling or a wall of a closed room having an 8 foot (2.4 m) high ceiling. For a QR sprinkler, the room is to be 15 by 15 feet (4.6 by 4.6 m). For a QR extended coverage sprinkler, the room size is to be as specified by the manufacturer and be the same dimensions used for the extended coverage tests in these requirements. The sprinkler inlet waterway is to be filled with water having a temperature of 70±3° F.(21±1.6° C.). The water is to be pressurized to 4½±½ psig (31±3.4 kPa), when required for sprinkler operation.
19.5.5 The fire source is to consist of a 1 by 1 by 1 foot (305 by 305 by 305 mm) sand burner located in one corner of the room with a flow of natural gas of 500 standard cubic feet (14.2 m3) per hour for ordinary temperature rated sprinklers and 600 standard cubic feet (17.0 m3) per hour for intermediate temperature rated sprinklers. A pendent, upright, or ceiling type sprinkler is to be installed along a diagonal line on the ceiling at a distance of 16 feet, 9 inches (5.1 m) from the corner of the room where the sand burner is located. A pendent, upright, or ceiling type extended coverage sprinkler is to be installed in the intended position at a point where a diagonal line from the corner having the burner to the opposite corner intersects an arc having a radius equal to the distance from the corner having the burner to the midpoint of the opposite wall. A sidewall sprinkler is to be installed on the midpoint of the furthest wall furthest the corner having the sand burner. The test is to be started when the ambient temperature is 87±2° F. (31±1° C.) for ordinary temperature rated sprinklers and 120±2° F. (49±1.1° C.) for intermediate temperature rated sprinklers, as measured in the center of the room 10 inches (254 mm) below the ceiling. The gas burner is to be ignited, and the operation time of the sprinkler is to be recorded.
The leakage test of Section 14 of UL 199, referenced in Section 23 is as follows:                14 Leakage Test        14.1 When tested as described in 14.2 and 14.3, an automatic sprinkler shall not exhibit leakage at any pressure from 0 to the applicable leakage test pressure shown in Table 14.1.        14.2 At least 20 samples are to be individually tested. The sprinkler inlets are to be filled with water and vented of air.        14.3 The pressure is to be increased from 0 to the test pressure at a rate not exceeding 300 psig (2.07 MPa) per minute and then held for 1 minute. There shall be no visible leakage in any sample.        
Table 14.1, referenced in Section 14.1 is reproduced herein as FIG. 4.
Section 26, entitled Impact Resistance Test states as follows:                26 Impact Resistance Test        26.1 An automatic sprinkler shall not be damaged or leak when tested as described in 26.2. See FIG. 26.1.        26.2 Five sample ½-inch nominal orifice sprinklers are to be tested by dropping a cylindrical mass equivalent to the mass of the sprinkler to the nearest 15-g increment from a height of one meter onto the geometric center of the deflector or, when this is not practicable, onto the butt end of the sprinkler. The mass is to be prevented from impacting more than once upon each sample. Following the impact, each sprinkler is to be visually examined and there shall be no evidence of cracks, breaks, or any other damage. Each sample sprinkler shall then withstand a 435 psig (3 MPa) hydrostatic pressure for 1 minute without leakage. In addition, each sample shall then be subjected to the Sensitivity—Oven Heat Test, see 19.2.1-19.2.5, and shall operate at within a 1.3 multiple of the mean time obtained on samples not subjected to the Impact Resistance Test.        
FIG. 26.1, referenced in § 26.1 is reproduced herein as FIG. 5.
Section 28 of UL 199 is as follows:                28 Vibration Test        28.1 An automatic sprinkler shall withstand the effects of vibration without deterioration of its performance characteristics. The sprinkler is to be subjected to vibration of 0.04 inch (1.0 mm) amplitude for 120 hours at a frequency that is continuously varied between 18 and 37 hertz. However, when the sprinklers exhibit a resonance at a frequency within the range of 18 to 37 hertz, the resonant frequency is to be used for the entire test period. Following the vibration test, the sprinkler shall comply with the Leakage Test, Section 14. In addition, the sprinkler shall operate as intended when subjected to the Sensitivity—Oven Heat Test, see 19.2.1-19.2.5.        28.2 Five sprinkler samples are to be threaded into the pipe couplings on a steel mounting plate, and the plate is to be bolted to the table of a vibration machine so that the sprinklers are mounted vertically. When dry sprinklers are tested, they are to be samples of the maximum length. The test sprinklers then are to be vibrated in the vertical direction.        28.3 This test is to be conducted with the test sprinklers unpressurized.        28.4 For these tests, amplitude is defined as the maximum displacement of sinusoidal motion from position of rest to one-half of the total table displacement; resonance is defined as the maximum magnification of the applied vibration.        
Section 35 is as follows:                35 10-Day Corrosion Test        35.1 The external parts of an automatic sprinkler shall withstand an exposure to salt spray, hydrogen sulfide, and carbon dioxide-sulfur dioxide atmospheres when tested in accordance with 36.1.4-36.5.1 for ten days each. Following the exposure:                    a) The Sensitivity—Oven Heat Test is to be conducted on sprinklers other than QR recessed, QR concealed, QR-EC recessed and QR-EC concealed types, see 19.2.1-19.2.5;            b) The Sensitivity—Room Heat Test is to be conducted on QR recessed, QR concealed, QR-EC recessed and QR-EC concealed type sprinklers, see 19.3.1-19.3.5; and            c) The Response Test for Ordinary and Intermediate Temperature Rated Ceiling Type Sprinklers is to be conducted on standard response type ceiling sprinklers, see 19.3.1-19.3.5.                        Each sample shall be operable, and the average time of operation shall not increase more than a 1.3 multiple when compared with the average time of operation of samples not subjected to the 10-Day Corrosion Test. During the corrosive exposure, the inlet thread orifice is to be sealed by a plastic cap after the sprinkler has been filled with de-ionized water.        35.2 A dry pendent or dry ceiling sprinkler that uses an operating assembly of the same type that has complied with the operation requirements specified in 35.1 shall be subjected to the plunge test specified in 35.3. After the heat-responsive element operates, all parts shall clear the waterway under an air pressure of 10 psig (69 kPa).        35.3 The plunge test is to be conducted in a full draft air oven that has been preheated to a temperature of 300±5° F. (149±3° C.) or a temperature of 100° F. (55.6° C.) higher than the marked temperature rating, whichever is higher. Each sprinkler is to be individually connected to a 10 psig (69 kPa) air supply and quickly placed in the oven in the pendent position.        
Sections 36.1.4 through 36.5.1 referenced in Section 35.1 is as follows:                36.1.4 Three groups, each consisting of five sample sprinklers, are to be assembled. One group is to be exposed to 20 percent salt spray, the second to hydrogen sulfide, and the third to sulfur dioxide-carbon dioxide.        36.1.5 CAUTION—Hydrogen sulfide and sulfur dioxide are both toxic gasses. Hydrogen sulfide gas is also flammable. Because of this, such gasses must be stored, transferred, and used only with gastight systems. Adequate ventilation must also be provided to handle any accidental leakage. Presence of these gases is readily noticeable. Due to their unpleasant order and irritant effect, they give warning of their presence.        
The entire UL 199 (10th Ed., 1999) is hereby incorporated herein by reference.
Still another organization recognized by the sprinkler industry, and various insurance and government bodies as providing definitive guidelines for the design of automatic sprinklers is the Factory Mutual Research Corporation (“FMRC”). FMRC's Approval Standard for Automatic Sprinklers for Fire Protection, Class Series 2000, May 1998, Section 1.9 defines a QR sprinkler as follows:                A sprinkler having an RTI equal to or less than 90 (ft·s)1/2[50(m·s)1/2], and a C-factor equal to or less than 1.8 (ft/s)1/2[1.0 (m/s)1/2]. For recessed, flush and concealed sprinklers the criteria outlined in Sections 4.30 or 4.31 must be met, as appropriate.        
A C-factor is defined as:                A measure of the conductance between the sprinkler's heat responsive element and the other components of the sprinkler expressed in units of (ft/s)1/2 or (m/s)1/2.        
Section 4.30, referenced in the definition of a quick response sprinkler is as follows:                4.3 Sensitivity (Recessed, Flush, and Concealed Types)        4.30.1 Requirements        Both standard and quick response recessed, flush and concealed automatic sprinklers shall operate within the maximum response times as calculated in Section 4.30.2(A) when tested as detailed in Section 4.30.2(B), in the least protrusive position as possible. Recessed, flush, and concealed extended coverage light hazard sprinklers shall comply with the requirements of Section 4.31. All of the test points must pass the stated criteria.        4.30.2 Test/Verification        A. The maximum response time shall be calculated using the combination of RTI and C-factor shown in Table 4.30.2(a) and the plunge tunnel conditions detailed in Table 4.30.2(b) for the respective response category.        The maximum permitted sprinkler operating times can be calculated using the following equation:      t    max    =                    (                  -          RTI                )            ⁢              (                  1          ⁢                      n            ⁡                          [                              1                -                1                -                                  Δ                  ⁢                                                                           ⁢                                                                                    T                        b                                            ⁡                                              (                                                  1                          +                                                      C                            /                                                                                          (                                u                                )                                                                                            1                                /                                2                                                                                                                                    )                                                              /                    Δ                                    ⁢                                                                           ⁢                                      T                    g                                                              ]                                      )                                      (          u          )                          1          /          2                    ⁢              (                  1          +                      C            /                          u                              1                /                2                                                    )                    where:        tmax=Maximum Allowed Response time of sprinkler, seconds        RTI=Response Time Index from Table 4.30.2(a), (ft·s)1/2 [(m·s)1/2]        ΔTb=Upper temperature limit of the sprinkler (1.035×nominal temperature rating) minus the ambient temperature, ° F. (° C.)        C=Conductivity factor from Table 4.30.2(a), (ft/s)1/2 [(m/s)1/2]        u=Air velocity in the test section of the tunnel from Table 4.30.2(b), ft/s (m/s)        ΔTg=Air temperature corrected for radiation effects on a the temperature sensing device, in the test section (see table 4.30-2(b)) minus the ambient temperature, ° F. (° C.)        B. Compliance with the requirements for maximum operating time shall be determined by operating sprinkler samples in the FMRC plunge tunnel, using the modified plunge tunnel test plate described in FIG. E-8.        The sprinklers shall be tested in both the best case orientation and the worst case orientation as if the sprinkler was a pendent sprinkler. For the worst case orientation, the angular offset shall be 15° for standard response sprinklers and 25° for quick response (see Table 4.30.2(a)).        A vacuum in accordance with Table 4.30.2(b) shall be applied to and maintained in the upper enclosure of the modified plunge tunnel test plate (FIG. E-8). The test shall be repeated three times at each condition to ensure accuracy and product repeatability.        
Tables 4.30.2(a) and 4.30.2(b) referenced in Section 4.30.2(A) are reproduced herein as FIGS. 6 and 7, respectively. FIG. E-8, referenced in Section 4.30.2(B) is reproduced herein as FIG. 8.
The entire FMRC Approval Standard for Automatic Sprinklers for Fire Protection, Class Series 2000, May 1998, is hereby incorporated herein by reference. Foreign countries have similar organizations which provide guidelines and criteria for the design and installation of sprinkler heads such as, for example, BRE Certification Limited in the United Kingdom, and Verband der Sachuersicherer in Germany.
As the foregoing guidelines make clear, a quick response sprinkler head must exhibit an increased thermal sensitivity. In most instances, because of the unacceptable response times of fusible links, the industry has been relegated to using a frangible glass bulb trigger assembly. The glass bulb trigger assembly, in contrast to most lever type trigger assemblies, is capable of exhibiting the sensitivity necessary to identify the sprinkler head in which it is used as a quick response sprinkler head. The manufacturing complexity of encasing a fluid with a known thermal expansion profile within a glass bulb having sufficient strength to withstand a compressive load imparted by the compression screw makes the glass bulb trigger assembly relatively expensive to manufacture. Furthermore, the materials necessary to manufacture the glass bulb trigger assembly also increases the cost of manufacturing.
Consequently, there exists a need within the industry for a trigger assembly capable of withstanding the direct compressive load imparted by the compression screw which is cost effective to manufacture, and exhibits the requisite performance characteristics necessary to be classified as a quick response sprinkler head.